Supporting track elements of this type are used in linear ball bearings. Linear ball bearings are known for the mounting of machine parts which are movable to and fro. Examples thereof may include a driving spindle and a bearing housing of a machine tool. The linear ball bearings have the task of ensuring friction-free mounting in the direction of movement. In order at least to ensure a satisfactory function even in the event of relatively small alignment errors occurring between the parts moving in relation to one another, the supporting track elements of the linear ball bearings have at least one radial outer surface which is outwardly curved at least in one direction (convexity) for contact with an inner surface of the part surrounding the guide rail. As a result, the supporting track elements can move in a tilting manner on the contact surface of the part surrounding the guide rail and alignment errors can be largely compensated for by said construction.
The production of the abovementioned convexity of the supporting track elements is comparatively costly. The convexity is generally produced by bending the supporting track elements in the desired direction. Due to the bending which has taken place, the supporting track element tracks lying opposite the convex outer surface still have to be ground in order to obtain the desired track quality. Sometimes, a further hardening of the supporting track elements is also provided.
The invention also relates to a linear ball bearing for the longitudinally displaceable mounting of a shaft-like guide rail in a part surrounding the guide rail, with a sleeve-like cage which has recesses which are arranged one behind another in the circumferential direction and in which recirculating ball tracks are held, wherein each recirculating ball track has at least one supporting section with load-bearing balls supported rollably on the guide rail, and wherein the load-bearing balls of a recirculating ball track are additionally supported rollably on a track of a supporting track element which is inserted indirectly or directly into the cage and has at least one radial outer surface which is outwardly curved at least in one direction and is intended for contact with an inner surface of the part surrounding the guide rail.
WO 01/11251 A1 (DE 199 37 278 A1) discloses a linear ball bearing. The latter has supporting track elements of the type in question which have an outer surface which is outwardly curved in two directions, and can therefore roll very readily in a pivotable manner on the bore inner surface of a machine housing surrounding the linear ball bearing. In addition, the supporting track elements are held in housing-like receiving parts which, for their part, are arranged such that they can be inserted in the radial direction into and removed from recesses in a sleeve-like cage.
DE 39 10 469 A1 describes a linear ball bearing in which supporting track elements are likewise inserted into recesses in a cage. The outer surface of the supporting track elements which is intended for rocking contact with an inner circumferential surface of a bearing housing bore receiving the cage descends radially inwards with respect to the cage axis from a central region, which is positioned in the region of the rocking axis of said outer surface, towards the ends of the supporting track elements.
DE 1 949 182 A1 also discloses a linear ball bearing in which use is made of supporting track elements which are beveled in their longitudinal direction from the center toward the ends and are inserted into recesses in a cage. The central part of the supporting track elements forms an axis of rotation and therefore permits a tilting movement, as a result of which angle errors between the parts moving in relation to one another can be compensated for.
DE 199 54 387 A1 likewise describes a linear ball bearing for the mounting of a shaft with supporting track elements, the radial outer surfaces of which are of curved design such that the supporting track elements can be adjusted by tilting to dimensional tolerances of the shaft.
Finally, mention should also be made of U.S. Pat. No. 5,558,442 which describes a linear ball bearing with supporting track elements which, in their central region, as seen in their longitudinal extent, have a radial outer surface which is curved in its longitudinal direction, the curvature extending over the entire width of the supporting track elements.